Prior to introduction of polyglycolide (PG) as braided synthetic absorbable sutures, surgical gut suture (SGS) was the choice suture for many surgical procedures. Although the PG suture was a strong competitor to SGS, the latter remained desirable in specific procedures because of its pseudo-monofilamentous form, knot security, and absorption profile. Even after introducing several monofilament sutures over the past two decades, the use of SGS was slightly affected. This is because of the fast absorption profile of SGS in comparison to all synthetic monofilament sutures. However, new concerns about bovine spongiform encephalopathy (BSE) and its relevance to the use of SGS and its undesirable high tissue reactions threaten its clinical viability. This justified exploring the development of a new synthetic absorbable suture that displays most attributes of SGS without contending with its unwanted tissue reaction and risk of BSE. Phase I objective is to determine feasibility of developing an absorbable, compliant monofilament suture having (1) similar handling and knot properties to SGS; (2) an initial holding strength superior to SGS; and (3) considerably faster absorption profile than present monofilament sutures. Phase I plans entail (1) designing a new class of block copolyesters based on a unique form of prepolymers and preparation/characterization of candidate copolymers, (2) monofilament spinning of selected copolymers and evaluating their in vitro properties as absorbable sutures; (3) identifying two most promising candidate sutures and evaluating their in vivo strength retention profiles and tissue reaction; and (4) preparing Phase II plans, which will include process development and scale-up of a selected suture and initiating needed studies to meet FDA regulatory requirements. PROPOSED COMMERCIAL APPLICATION: Successful completion of Phase I will (1) provide the basic data for development of a clinically equivalent or superior substitute to surgical gut in Phase II; (2) demonstrate the viability of using a novel concept in macromolecular chain design to develop new absorbable materials for known and new applications; and (3) yield new critical data pertinent to the novel use of low- dose radiation sterilization and autocatalysis in producing absorbable surgical implants and scaffolds for tissue engineering.